This invention relates to apparatus for forming surface patterns upon the surface of an uncured concrete slab, and more particularly relates to a wheel-like apparatus having a worker therein to provide some of the downward driving forces, as well as propulsion and directional control, the wheel having pattern forming blades therearound which penetrate the surface of the slab to provide the patterns.
Some years ago I invented a method of manufacturing bricks, tiles, cobblestones and the like by driving forming blades into the plastic surface of a freshly cast slab of concrete to form grooves therein and later filling the grooves with a grout of mortar. That method is described in U.S. Pat. No. 3,406,618 which issued to me on Oct. 22, 1968. While that method has been successfully utilized to form bricks, tiles and cobblestones and the like on floor and walking surfaces, its implementation has had a number of drawbacks.
The tools which formed the patterns in the practice of my invention were flat, snowshoe-like grids which weighed approximately forty pounds apiece. Those grids were provided with handles and striking anvils and had to be manually lifted into place and then driven by blows from a hammer to force the blades on the underside of the grid into the surface of the concrete. The tremendous forces required to sink the grid blades into the concrete surface stemmed directly from the relatively large area of the grid blades in contact with the concrete surface. Also, those tools were heavy to lift and difficult to realign during the pattern making operation. The hammer driven technique of using those grid tools not only was slow and tedious but also resulted in the concrete tending to become set up before the pattern was completed. Consequently, my original techniques invited tool breakage and failures resulting from attempts to complete the pattern after the slab had become set and too hard to work.
Another drawback of my original grid tool was its creation of small ridges of concrete between otherwise linearly aligned grooves which occurred between adjacent patterns formed by the grid tool. As the tools were positioned and driven into the slab, unpatterned concrete surfaces were left where the tools would not or could not touch each other when driven into the surface. Those unwanted ridges resulting from the misalignment of the tools were usually removed after hardening of the slab, e.g., by manually chipping and breaking with a hammer and chisel and then manually collecting chipped fragments. The drawback of the unwanted ridges is overcome by my present invention.
Still another drawback of my grid tools were that they tended to bounce away from each other when driven into the concrete surface. This tendency not only resulted in the undesirable ridges, it also adversely affected alignment of the pattern.
A further drawback was that for large slabs, or example, fifty thousand square feet, the pouring and finishing contractors has to treat the construction as a series of small slabs, for example, fifty separate pours and finishes which made my prior method slow and often prohibitively expensive for those larger slabs.
The imprinting tool I invented for forming nonrepeating stone patterns in fresh concrete (described in U.S. Pat. No. 3,807,888, issued to me on Apr. 30, 1974), had the same drawbacks and limitations as my grid-like tools, particularly for large slabs of thousands of square feet. It was a manual tool that had to be put repeatedly in place and driven into the surface of the slab.
One user of my pattern-forming system, William V. Moorhead, proposed to overcome the above-mentioned drawbacks and limitations of my manually driven pattern forming tools by axle-mounting a pattern roller to a tractor frame and providing a release agent, such as plastic film, between the blades of the roller and the still plastic concrete surface. His apparatus and processes are described in his U.S. Pat. No. 3,832,079, issued Aug. 27, 1974. One inherent drawback of the Moorhead invention was that the cross sectional diameter of the roller was much too small in relation to the depth of penetration required of the pattern-forming blades secured thereto. As the roller traveled across a freshly poured slab, the blades bent, tore, and broke the concrete edges at each penetration. The provision of the conventional release mechanism of the plastic film reduced the tearing and breakage at the edges of the grooves somewhat, but had the undesirable effect of rounding the concrete mass between the grooves which made the finished floor surface difficult, uncomfortable, and perhaps unsafe to walk upon. Moreover, the tractor device disclosed in the Moorhead U.S. Pat. No. 3,832,079 if ever built, would have been unwieldy and very difficult to maneuver into position and to operate, and would have tended to become bogged down in the freshly poured concrete. It would have been a very expensive device to manufacture and maintain, and difficult to operate properly. The Moorhead concept was generally not well accepted in the trade and was limited to usage in conjunction with the plastic release film. It was a fixed-width roller and as such had all of the prior art disadvantages associated with the surface patterning of slabs substantially wider than the roller.